Improvement in parallel rulers



.E. J. TOWNE.

PARALLEL RULERS. I I 7,330. Patented Feh.13,1s7*r..

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WITNESSES:

NLPETERS, FHUTO-LITROGRAFNER, WAHING'TON. D. C.

v"- m ANA UNITED STATES PATENT Ormon.

EUGENE J. TOWNE, OF NORTH DANA, MASSAOHUSETTS, ASSIGNOR TO HIMSELF AND J. W. GOODMAN, OF SAME PLACE.

IMPROVEMENT IN PARALLEL RULERS.

Specification forming part of Letters Patent No. 187.330, dated February 13, 1877; application filed December 23, 1876.

To all whom it may concern:

Be it known that I, EUGENE J. ToWNE, of North Dana, in the county of Worcester and State of Massachusetts, have invented a. new and Improved T-Square, of which the following is a specification In the accompanying drawing, Figure 1 represents a top view ofmy improved T-square, and Figs. 2 and 3 are, respectively, an end view and a vertical transverse section of the same on line 0 c, Fig. 1.

Similar letters of reference indicate corresponding parts.

The invention relates to an improved T- square that combines the advantage of acom mom and bevel square with a parallel ruler admitting parallel shading at any position of the blade in a convenient, quick, and accurate manner, and the invention consists of a T- square with adjustable blade, slidingv by its head in a recessed guidepiece attached to the drawing-board. The guide-piece carries in end-brackets a longitudinal screw-shaft that is operated by a thumb-rest, ratchet, and pawl, and an adjustable stop device, so as to move the blade by a split looking-nut at equal distances for parallel ruling.

In the drawing, A represents the head, and B the blade, of my improved T-squarc, which is capable of adjustment to any angle by the clamp-screw a, indicator 1), and a graduated protractor, d, attached to the head. The head A is moved into any position in a grooved guide-piece, G, that is attached by end-clamps and fastening-screws O to one side of the drawing-board. The clamps O are provided at the top parts with brackets, e, which carry a screw-shaft, D, that is turned by means of a spring-pawl,f, attached to a loosely-turning disk, g, with thumbrest g, the pawl engaging a ratchet, f keyed fast to the screw-shaft, and being retained in opposite direction by a checkpawl, f A projecting shoulder, 9 of disk 9 forms contact with a curved and slotted stop, h, that is adjusted by a set-screw, h, at the end of the clamp O, and defines, in connection with the clamp, the extent of swinging motion of the thumb-piece, and thereby the degree of rotation of the screw-shaft. The T-square is The turning of the screw-shaft by the thumb- 7 rest produces the parallel motion of the T- square with a greater or less distance between the lines, by the action of the split nut, and admits thereby the quick and accurate parallel ruling with the T-sqnare. By opening the nut and throwing the hinged sections clear of the screw-shaft the T-square may be used in the customary manner, and at any angle to the head.

The attachment forms a simple mechanism for parallel shading, and is operated by one hand, while the drawing-pen is held in the other hand for drawing the parallel lines in quick manner, and at any required distance from each other.

Having thus described my invention, I claim as new, and desire to secure by Letters Patent the head with a screw-shaft and revolving mechanism, operated by the thumb to produce the parallel motion of the blade, substantially in the manner and for the purpose set forth.

2. The combination of a revolving screwshaft, D, having fast end-ratchet with a loosely-swinging thumb-rest, spring-pawl, and check-pawl, substantially as specified.

3. The combination of the swinging ratchet thumb-rest, having projecting shoulder, with a slotted adjustable st0p-pieoe andset-screw to regulate extent of rotation of screw-shaft, substantially as set forth.

4.. The combination of the revolving screwshaft with a split nut, attached to head of the T square. the nut being made of hinged and spring-locked sections to be attached or detached from screw-shaft, as required for the purpose set forth.

EUGENE J. TOWNE. Witnesses:

ALPHEUs J. NYE, ALLEN W. GOODMAN.

l. The combination of a guided and adjustable T-square having a split nut, attached to 

